1. Field of the Invention
This invention relates to a radio telephone system control apparatus and a method for controlling the connection of a base unit connected to a wired telephone channel and a plurality of radio telephone handsets connected to the base unit through radio channels, and more particularly an apparatus for controlling an intercom connection among a plurality of the radio telephone handsets.
2. Description of the Related Arts
Radio telephone systems comprise a base unit connected to wired telephone lines and one or more radio telephone handsets connected to the base unit through radio channels, such as a cordless telephone. The cordless telephone apparatus consists of a base unit connecting apparatus connected to wired telephone channels, and a radio telephone handset provided for the base unit in a one to one correspondence, and the frequencies of its signals are fixed such that up radio channels from the radio telephone handsets to the base unit utilize signals of frequency f.sub.1, while down telephone channels from the base unit to the radio telephone handsets utilize signals of frequency f.sub.2. As a consequence, where two radio telephone handsets are utilized, it is necessary to install two base units.
With such a radio telephone system utilizing two radio telephone handsets and two base units, however, two radio telephone handsets are not usually used simultaneously, so that provision of two base units is not economical.
In recent years, for the purpose of efficiently utilizing allocated frequencies, a so-called multi-channel access system has been adopted wherein a frequency being used is determined by utilizing a common channel, for example, a control channel between a plurality of base units, and then the channel is switched to a speech channel corresponding to the frequency. However, when such a multi-channel access system is adopted, there is a problem in the case where a base unit is provided for each of the two radio telephone handsets that when a ring signal is received from a wired telephone handset, the two base units start connection control using respective control channels simultaneously, whereby radio waves from these control channels interfere with each other. Thus, the connection control is sometimes made impossible.